ISSN : 1225-3480
This study was focused to know what happened to three bivalve resources (Ruditapes philippinarum, Mactra veneriformis, and Meretrix petechialis) at tidal flats around the Saemangeum during recent years. The population density of M. petechialis at the Yubu-do tidal flat has been gradually declined by the continuous harvesting of fishermen and reached to be a very low density of 0.6 ind./m2 . Because a very low juvenile recruitment is expected due to the lack of larval supply from a very low fertilization rate due to its low adult density, it is necessary to provide some protective sites containing dense adults of M. petechialis in order to avoid the Allee effects in Yubu-do tidal flat. In the case of the populations of R. philippinarium and Mactra veneriformis at Wi-do tidal flat, there was no natural recruitment during recent two years and few small individuals of these two species and only large individuals were found compared with those from Yubu-do and Sinshi-do, especially at the lower tidal flat due to the accumulation of fine sediments. For Ruditapes and Mactra populations, it should be necessary for a detailed a detailed monitoring study to solve problems on the survival of juveniles and recruitment failure and to know whether there are some relationships between the high mortality and recruitment failures and fine particle depositions at the tidal flats.
In this study, we evaluated the effect of inland pollution sources on sea water and oyster (Crassostrea gigas) in JaranmanㆍSaryangdo area after rainfall events. We analyzed the sanitary indicator microorganism such as coliform group, fecal coliform and Escherichia coli (E. coli) in the discharge water of major inland pollutants, sea water and oyster for 3 days after 24.5, 50.0 and 67.5 mm rainfall events. As the rainfall in this area became increased, the range of fecal coliform of 15 contaminants was increased gradually (24.5 mm; 4.5-54,000 MPN/100mL, 50.0 mm; < 1.8-92,000 MPN/100mL, 67.5 mm; 49-240,000 MPN/100mL). However, the range of radius of impacted area of 15 contaminants was decreased and getting better for 3 days. The peak pollution was observed in the Yongho-village domestic waste water. The calculated impact area of inland pollution sources was 0.03 km2 immediately after 24.5 mm rainfall and expanded to 0.2 km2 after 67.5 mm rainfall. These calculations of impacted area matched results from fecal coliform analyses with sea water. According to the evaluation of the influences of inland pollution sources and fecal coliform analyses on sea water and oyster this area, pollutants from inland sources did not reach the boundary line of the oyster growing area after rainfall events. The bacteriological water quality of the oyster growing this area met the Korea standard and US NSSP requirements for approved oyster growing area. And the E. coli level of oyster at 10 station in the designated area was met the EU regulation and the limit of raw oyster in Korea with ranged from < 18 to 230 MPN/100g.
This study was conducted to measured the survival rate (or mortality) of Ruditapes philippinarum according to the change of salinity when the water temperature is high. In laboratory, the mortality test was performed on the R. philippinarum, we conducted experiments at water temperature 20, 25, and 30℃, salinity was tested at intervals 5 psu from 0 to 35 psu. As a result of exposure for bottom water of Bunam lake, the mortality was 20% in 100% bottom water, and it was found that there was no effect at concentrations below 50% in bottom water in Bunam lake. The LC50 by water temperature was 4.816 psu at 20℃, 14,645 psu at 25℃, and 20.063 psu at 30℃. The death of the clam was observed only at a concentration of 15 psu or less at 20℃. But the dead R. philippinarum observed at all concentrations of salinity at 30℃. The filtration rate was 0 ml min-1 at only 0 and 5 psu at 20℃, but the feeding activity started from 20 psu or higher at 30℃. As such, exposure to low-salinity water during the high-temperature period has an effect on the filtration rate and mortality of R. philippinarum.
Solen grandis is an industrially important edible bivalve that is traded at high prices as it is unfarmed and the production has decreased due to environmental pollution and overfishing. Major studies on Solen grandis have reported only basic research on reproductive development, change, etc., and no studies on spawning, egg development, and larval management have been reported for seed production and aquaculture technology development. Therefore, in this study, spawning was carried out using mature plaques secured through habitat survey for Solen grandis seed acid, and artificial seed production was succeeded, and the egg development process from fertilized egg to D phase larva and larval development process of 1 mm or more were observed through a microscope. Additionally, this study aims to develop technology for promoting seed production as basic research for fostering high value-added bivalve industrial varieties and resource recovery. Based on the existing research data, we conducted research on the development of fertilized eggs and larval development using the mature plaques of Solen grandis.
This study was conducted for the purpose of estimating the genetic improvement and effects of selection on growth traits of Pacific Abalone, Haliotis discus hannai. For the analysis, 2,733 individuals of 5th generation of selective breeding produced in 2017, their pedigree data and phenotypic data of growth traits at the age of 30-months. Genetic parameter, heritability, and breeding value were estimated by the Best linear unbiased prediction (BLUP) method using REMLF90, with sex treated as a fixed effect. At the age 30-months after hatching, the overall means of shell length, shell width, and total weight were 88.3 mm, 57.8 mm and 79.4 g, respectively. and the coefficient of variation of weight was 22.6%, showing the greatest variation among the three growth traits. A high level of significance was recognized as a result of ANOVA of growth traits for sex (P < 0.001). The heritability of shell length, shell width, and total weight were 0.315, 0.339, and 0.304, respectively. The higher the selection intensity, the higher the expected genetic improvement and selection effect. However, in order to minimize inbreeding while maintaining the genetic diversity of the population, selection intensity should be appropriately considered.
A duplex PCR primer set was developed for molecular biological species identification by making species-specific primers for Corbicula fluminea and Corbicula japonica distributed in Korea. The developed species-specific primers were designed to form an interspecies-specific band around C. fluminea 289 bp and C. japonica 143 bp by searching for a site of interspecies genetic variation appearing on the nucleotide sequence of the cytochrome c oxidase subunit 1 (co1) gene of mitochondrial DNA. A verification experiment was also performed on the duplex PCR primer set by measuring the amplification efficiency for each repeat number and genomic DNA (gDNA) concentration. The duplex PCR primer set finally established was found to require a minimum of 10 ng/μL of gDNA concentration when considering the sample amount and PCR reaction cycle in terms of economic feasibility, and 30 cycles were found to be suitable. Therefore, the duplex PCR primer set between C. fluminea and C. japonica developed in this study is judged to be able to perform accurate species identification quickly and conveniently by PCR band observation.
The amount of data is growing very fast as advances in NGS technology enable the acquisition of large amounts of genome and transcriptome data. Moreover, the accuracy and speed of bioinformatic analysis of NGS data remains of great importance these days. However, the sequence database of mollusks is fall short of other organisms groups, and it thus appears that the annotation results after BLAST analysis are not accurate and reliable due to potential contamination with fungal sequences in mollusks sequence database. In this context, we constructed a BLAST database with 20 species of mollusk unigene sequences and 32 species of fungal sequences derived from previous studies. In order to confirm the contamination of fungal gene sequences in the unigenes of 20 endangered species, bioinformatics analysis was performed using BLAST. It reveals that the NGS sequences of mollusks are mixed with fungal sequences. Taken together, our results suggest that it is essential to reconfirm mollusks sequence information before publication.
